Ah sure I remember the time we moved from the abacuses to those new fangled punched card yokes. Great they were, and the valves looked lovely on a winters evening.
If you’re using internal drives the main disadvantage is that if you get heat problems in your computer itself it could fry all your drives. I like having them external as something that kills the main computer won’t kill the backups.
If you’re using eSATA then the drives are as fast external as they are internal. Just be aware of what Steve said and don’t buy the cheapest ones out there – the enclosures aren’t going to be well engineered. Go for something that has good heat-sink ability or is fan cooled.
You guys should consider off-site storage with a portable drive, team up with another photographer and store each others drive. A burst pipe/radiator or a fire or maybe a thief in your computer room is goanna screw even the most expensive industrial drive you can buy.
There is a good selection of storage systems on http://www.iomega.com.
They all come with backup software and orders over €149 are shipped free of charge.
You also get 2GB of free online storage with the software to backup those really important files. This can be upgraded to unlimited online storage for $5 per month.